Firstly, congratulations! It was quite a job organizing the 'arcgis' tag.
I believe we should definitely blacklist it.
Users will use the correct tag from now on (when typing 'arcgis', they will see the alternative tags and be able to make the correct choice, as mentioned by Sideshow Bob).
There will be less tag-editings bumping posts to the active page, ...
I think burnination is overkill for a tag that is so rarely used, but I certainly think that it should be removed from about half of its current questions because they already mention a product from the web tier.
I just added a tag excerpt and wiki for web-gis which hopefully will explain why I think it remains an occasionally useful tag:
I've started to create these when I see the same errors being asked about repeatedly.
If a specific error message is only present in a small number < 10 I would not consider creating. However, there are some that are getting up into the 50+ range, and with so many new users coming on board I see them as being likely to get into the "few hundred over ...